This invention generally relates to fragrance dispensing devices and, more particularly, to devices which dispense fragrance from an aroma bearing media by passing a current of warm air near or though the media to enhance diffusion of the fragrance into the adjacent air.
Operators of commercial buildings with interior spaces exposed to the public, and in particular hotel and motel operators, often desire to provide a consistent, pleasant fragrance in those spaces. A variety of devices and methods have been developed for dispensing, on a controlled basis, an appropriate fragrance into a room environment. For example, a number of devices have been developed which periodically dispense a gas or volatile liquid fragrance media from a closed container directly into the air. The fragrance media may be stored at elevated pressure and merely released, or may be actively pumped from the container. While these devices may be acceptable for some purposes, they are inappropriate for hotel guest rooms in that their periodic dispensing produces undesirable noise and sharp variations in the perceived strength of the fragrance. To be effective, these devices must be in an area of free air circulation, and thus are typically mounted in a prominent location on an exposed wall, which may be aesthetically objectionable.
To avoid these and other disadvantages, various fragrance dispensing devices have been developed which provide a continuously exposed fragrance bearing surface and which rely on natural diffusion of the fragrance media into the air, either unaided, or enhanced by temperature, air flow rate, or the like. At least one of these dispensers has a porous pad of cloth or the like which is impregnated with the fragrance bearing media. U.S. Pat. No. 4,804,821 discloses a diffusion dispenser using a fragrance-emitting block impregnated with an aroma bearing media. The block is located in a user-accessible chamber so that it may be conveniently replaced when the media is expended. A heater located below the block provides a current of warm air to enhance diffusion. The block has a number of chimney-like vents running vertically therethrough to permit the air current to flow through the block, thereby increasing the effective fragrance-diffusing surface area exposed to the air. The heater is thermostatically controlled using a sensor located above the heater when the diffuser is in its normal upright orientation. The diffuser has a rotating electrical supply plug to permit the diffuser to be installed in an upright orientation regardless of the orientation of an available wall outlet.
The diffusers of the prior art exhibit a number of significant disadvantages. One problem is safety. The thermostats of the prior art diffusers are located above the heater when the diffuser is installed in its normal orientation. Because convection air currents normally flow upward, if a diffuser is incorrectly installed, for example, in a non-upright orientation, the thermostat will be located below or to the side of the heater and will not be actuated by the rising current of warm air. Thus, the thermostat will permit the heater to operate continuously, possibly causing a fire or damage to the diffuser.
Another safety problem is the ease with which "foreign" fragrance blocks (i.e., a fragrance block not specifically designed to work in the particular diffuser, which may lack design features required for safe operation) and other foreign objects may be inserted into the heated fragrance block chamber. In prior art diffusers, any object which does not exceed the boundaries of the diffuser's heated fragrance block chamber may be inserted therein. An uninformed user who runs out of the intended fragrance blocks, for example, may be tempted to insert a fragrance block designed for a non-heated dispenser, or even a bar of soap. These objects may lack the necessary vent channels to prevent overheating of the heater element.
An analogous operational problem is presented by the desire of institutional users to provide a certain selected aroma in a particular area, and a different selected aroma in another area. It is difficult to ensure compliance with such desires by maintenance, housekeeping, or other personnel who may replace expended fragrance blocks, because prior art diffusers will accept any block which does not exceed the boundaries of the diffusion chamber.
Another operational problem with prior art diffusers is that their relatively high-temperature, thermostatically-controlled heaters operate intermittently, thereby causing noticeably sharp variations in the perceived fragrance intensity. Hotel and other public accommodations operators prefer that guests perceive a consistent level of pleasant fragrance, rather than occasional sharp fragrance bursts. A further operational disadvantage of the prior art diffusers is that their power supply plugs are so located that the diffuser housing obscures adjacent power receptacles, preventing use of those receptacles.
Prior art diffusers present a further operational problem in that they do not effectively indicate when the aroma-bearing media in the fragrance block is expended. U.S. Pat. No. 4,795,883 discloses a fragrance diffuser having a timer circuit which measures a predetermined period of elapsed time corresponding to the predicted life of the diffuser block, and when exceeded, presents a visual indicator or disables the heater. The timer is reset by a sensing switch actuated when a fragrance block is inserted or removed. This causes inaccurate results as the user may wish to remove the fragrance block before it is expended, for example, to inspect the block to determine which fragrance it contains, without starting a new timing period.
Disabling the heater after the timer has expired is undesirable because even after the predetermined period, the fragrance block will typically still contain a sufficient amount of aroma media to provide effective (if not optimal) air treatment. Disabling the heater thus prevents the diffuser from operating at all during the period between the timer expiration and the time the user notices the indicator, so that the room is entirely deprived of fragrance treatment during this period.
A further problem with prior art diffusers is related to the characteristics of the aroma-bearing cartridge. Due to the present chemistry of the cartridge, the apparent level of fragrance released from the cartridge is not constant over the life of the cartridge. An excessive fragrance level is particularly noticeable during the first few days after the installation of a new fragrance cartridge. Therefore, if a constant level of heat is applied to the cartridge over its life cycle, then the fragrance seems to be too strong at the beginning of the life cycle, and too weak at the end of its life cycle. This apparent changing of the fragrance levels, which is typical of most solid cartridge fragrance blocks, is highly undesirable.
Thus, a need exists for a method and means for controlling the fragrance level of a solid cartridge block over its life cycle.